Electric utility subsidiary - Unconsolidated variable interest entities (Details) $ in Thousands	1 Months Ended			3 Months Ended		6 Months Ended
	Oct. 31, 2004 MW	Mar. 31, 2004 USD ($) security	Oct. 31, 1988 MW	Jun. 30, 2015 USD ($) entity	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) agreement entity kW	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Power purchase agreement
Purchases from IPPs				$ 149,000	$ 188,000	$ 285,000	$ 353,000
Accounts payable				$ 183,094		$ 183,094		$ 186,425
Hawaiian Electric Company
Power purchase agreement
Number of power purchase agreements (PPAs) | agreement						6
Maximum capacity of small power production facilities (in kilowatts) | kW						100
Number of entities currently not required to be consolidated as VIEs | entity				0		0
Percentage of power purchase from AES Hawaii, Inc. (AES Hawaii), Kalaeloa Partners, L.P. (Kalaeloa), Hamakua Energy Partners, L.P. (HEP) and HPOWER						90.00%
Purchases from IPPs				$ 107,370	140,805	$ 210,620	264,774
Number of firm capacity producers declining to provide financial information to determine primary beneficiary status | entity						2
Minimum potential number of IPP entities consolidated into company in the future | entity						1
Hawaiian Electric Company | AES Hawaii, Inc. (AES Hawaii)
Power purchase agreement
Purchases from IPPs				26,000	36,000	$ 60,000	69,000
Hawaiian Electric Company | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Purchases from IPPs				48,000	74,000	92,000	141,000
Power purchase capacity that Increases from initial capacity (in megawatts) | MW			180
Number of years entity entered under power purchase agreement			25 years
Power purchase capacity that Increases from initial capacity (in megawatts) | MW	208
Accounts payable				14,000		14,000
Hawaiian Electric Company | Hamakua Energy Partners, L.P. (HEP)
Power purchase agreement
Purchases from IPPs				10,000	8,000	21,000	20,000
Hawaiian Electric Company | HPOWER
Power purchase agreement
Purchases from IPPs				16,000	16,000	32,000	32,000
Hawaiian Electric Company | Other IPPs
Power purchase agreement
Purchases from IPPs				49,000	54,000	80,000	91,000
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreement
Purchases from IPPs				24,555	28,170	46,448	57,661
Maui Electric
Power purchase agreement
Purchases from IPPs				17,359	$ 19,348	28,223	30,804
HECO Capital Trust III
Unconsolidated variable interest entities
Investment in 2004 Debentures				51,500		51,500		51,500
Interest income						1,700	1,700
HECO Capital Trust III | Hawaiian Electric Company
Unconsolidated variable interest entities
Principal amount of 2004 Debentures		$ 31,500
HECO Capital Trust III | Hawaiian Electric Company | 2004 Trust Preferred Securities
Unconsolidated variable interest entities
Number of 2004 Trust Preferred Securities issued | security		2,000,000
Dividend rate on 2004 Trust Preferred Securities (as a percent)		6.50%
Aggregate Liquidation preference		$ 50,000
Balance of Trust Securities				50,000		50,000		50,000
Dividend distributions on Trust Preferred Securities						1,600	1,600
HECO Capital Trust III | Hawaiian Electric Company | Trust Common Securities
Unconsolidated variable interest entities
Aggregate Liquidation preference		1,500
Balance of Trust Securities				$ 1,500		1,500		$ 1,500
Common dividend						$ 50	$ 100
HECO Capital Trust III | Hawaii Electric Light Company, Inc. (HELCO)
Unconsolidated variable interest entities
Principal amount of 2004 Debentures		10,000
HECO Capital Trust III | Maui Electric
Unconsolidated variable interest entities
Principal amount of 2004 Debentures		$ 10,000